Herpes zoster subunit vaccine may reduce rate of herpes zoster and postherpetic neuralgia in adults ≥ 70 years old

Postherpetic neuralgia is a complication of herpes zoster, especially for those of advanced age.

Vaccination to prevent herpes zoster currently consists of a single dose of a live attenuated vaccine and is recommended in adults ≥ 60 years of age.

In a recent randomized trial of immunocompetent adults ≥ 70 years old, a herpes zoster subunit vaccine reduced the rates of both herpes zoster and postherpetic neuralgia compared to placebo.

The incidence rate of herpes zoster (HZ) in the United States is estimated to be 10.5 per 1,000 person-years in adults ≥ 60 years of age (BMC Infect Dis 2015 Nov 6;15:502). Postherpetic neuralgia (PHN) is reported to occur in 10%-20% of patients with HZ who are ≥ 50 years of age (Int J Clin Pract 2009 Sep;63(9):1386). Zoster vaccination of adults ≥ 60 years of age is recommended by the Advisory Committee for Immunization Practices (ACIP). Currently, zoster vaccination in the United States consists of a single dose of a live attenuated vaccine, which in the Shingles Prevention Study had a vaccine efficacy of 51.3% (95% CI 44.2%-57.6%) for the prevention of HZ and 66.5% (95% CI 47.5%-79.2%) for the prevention of PHN at a median follow-up of 3.1 years (N Engl J Med 2005 Jun 2;352(22):2271). In the ZOE-50 trial, an HZ/subunit (su) vaccine has been shown to have a vaccine efficacy of 96.2% (95% CI 92.7%-98.3%) for the prevention of HZ in adults ≥ 50 years of age (N Engl J Med 2015 May 28;372(22):2087). A recent trial conducted at the same international sites as the ZOE-50 trial investigated the efficacy of this HZ/su vaccine for the prevention of HZ in 14,816 immunocompetent adults ≥ 70 years of age randomized to either two-dose vaccination or placebo doses administered by intramuscular injection two months apart. Follow-up was for a mean of 3.7 years. The ZOE-70 trial also reported on the efficacy of the HZ/su vaccine to prevent PHN by pooling data with an additional 3,631 adults ≥ 70 years old from the ZOE-50 trial.

Among the adults receiving at least one dose of vaccine or placebo, the total number of cases of HZ from the ZOE-70 trial was 270 and the number of PHN cases from the combined ZOE-50 and ZOE-70 trials was 46. In adults receiving at least one dose, the incidence of herpes zoster was 1.1 per 1,000 person-years with HZ/su vaccine vs. 9.1 with placebo (adjusted vaccine efficacy 87.7%, 95% CI 82%-92%, NNT 35) with similar results in adults receiving both doses. Combining data from the ZOE-50 and ZOE-70 trials, the incidence of PHN in patients receiving at least one dose was 0.2 per 1,000 person-years with HZ/su vaccine vs. 1.1 with placebo (adjusted vaccine efficacy 78.9%, 95% CI 54%-91.5%, NNT 314) and in patients receiving both doses the incidence was 0.1 vs. 1.2 (adjusted vaccine efficacy 88.8%, 95% CI 68.7%-97.1%, NNT 279). In a randomly selected subgroup of 1,025 patients, injection-site reactions > 100 mm in diameter occurred in 8.5% of the vaccination group vs. 0.2% of the placebo group (p < 0.05, NNH 12) and systemic reactions such as fatigue, myalgia, headache, shivering, fever, and gastrointestinal symptoms preventing normal activity occurred in 6% vs. 2% (p < 0.05, NNH 25).

This trial demonstrates that the HZ/su vaccine provides significant protection against HZ and against PHN for more than three and a half years in adults ≥ 70 years of age. Sizable injection-site reactions and systemic symptoms impeding normal daily activity were more common with the vaccine and have the potential to impact compliance with the two-dose regimen in clinical practice. Although the data suggest that the new HZ/su vaccine may be more effective than the live attenuated HZ vaccine, this conclusion is limited by the lack of a direct comparison in a head-to-head trial and the low number of incident cases of PHN. Finally, the reduction in postherpetic neuralgia, while substantial in relative terms, is small in absolute terms.

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